Lead poisoning induces nuclear bodies, composed of lead and protein, in many animals including man. These bodies are prominent in hepatic cells and in real tubular lining cells. Humans are exposed to lead from environmental sources. Much attention has been focused on the eating of lead-containing paint flakes by children, the emission of lead from automobile exhausts, and the exposure of industrial workers. There are well-known clinical effects of lead poisoning, but neither the function nor the effect of the nuclear inclusion bodies is known. We have identified three nuclear acidic proteins which probably serve a fundamental structural function in most cell nuclei. They are excellent candidates for involvement in the inclusion bodies because of certain chemical properties. Methods are now available to permit direct comparison of the nuclear-inclusion body protein with these structural proteins as well as proteins in other nuclear fractions. Identification of the specific proteins in the inclusion bodies is a first step in understanding their role. We propose to examine inclusion bodies in rats for the presence of these three specific polypeptides as well as proteins from other nuclear fractions. The synthesis of the specific polypeptides in the inclusion bodies will be examined during lead-induced inclusion body formation in mice. Synthesis of the polypeptides under these conditions will be compared with their synthetic rate in the absence of lead exposure in order to determine the extent to which lead intoxication alters nuclear protein metabolism.